Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 140447
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1147 PM CDT Sun Apr 13 2014

.DISCUSSION...
ISSUED 900 PM CDT Sun Apr 13 2014

Latest surface analysis has low pressure centered over extreme
west central Illinois, with the trailing cold front extending into
the southern plains. Scattered showers have continued to impact
the forecast area early this evening, with a few embedded
thunderstorms. The more widespread showers/storms along the cold
front have been on a downward trend of late with respect to both
coverage and intensity, and with the loss of diurnal heating this
trend is likely to continue.

Current forecast has rest of night pretty well covered. However,
plan to tweak the forecast for the latest trends, mainly to reduce
thunderstorm mention and lower precipitation amounts.

Bak
&&

.AVIATION...
ISSUED 1147 PM CDT Sun Apr 13 2014

Cold front pushing into west central Illinois at the moment, and
will be clearing the central Illinois terminals over the next few
hours. The rainfall threat has largely ended across the terminals,
although it is still possible for a few more hours at KDEC & KCMI.
VFR and spotty MVFR conditions will quickly fall to widespread low
end MVFR (and possibly briefly to IFR), in the wake of the cold
front. An upper level disturbance behind the main system will
bring a chance of light snow to the terminals late Monday
afternoon into the evening, but significant snow is not
anticipated. Gusty southerly winds ahead of the front will swing
around to the north behind the front, remaining gusty for most of
the 06Z TAF valid time.

Bak
&&

.PREV DISCUSSION...
ISSUED 200 PM CDT Sun Apr 13 2014

SHORT TERM...Tonight through Wednesday

Best threat for widespread showers and thunderstorms to occur
across the area tonight into Monday morning before a change to
much colder weather and a chance of snow Monday afternoon and
evening.

Surface low pressure forecast to push out of Kansas and track
northeast into north central Illinois by late this evening. Models
continue to indicate two areas of enhanced lift/convergence, the
first area over our northwest where the surface low will track
along a stalled frontal boundary, with a secondary area of forcing
shifting NNE out of Arkansas into south central Illinois late
tonight. Instability not overly impressive across the forecast
area with the better combo of instability and shear remaining to
our southwest. However, forecast soundings indicating strong wind
fields just above 925 mb this evening out of the south so any
storm that has a sustained updraft may be able to bring some of
the stronger winds down to the surface, especially just ahead of
the surging cold front late this evening. As far as the heavy
rains are concerned, we missed out last night with most of the
more significant rains remaining to our northwest, but it appears
tonight into Monday morning we could see from 1 to 2 inches,
especially along and west of the Illinois River.

Temperatures will be on the mild side thru a good portion of the night
most areas, but just after midnight we should see the surface low
shift to our north allowing the cold front to surge east across
the forecast area during the early morning hours. Deep cyclonic flow
and strong cold advection will bring windy and much colder weather
to the area on Monday with showers during the morning with the rain
gradually mixing with or changing over to light snow during the
afternoon north, and over the southeast by evening. Still not looking
like much in the way of accumulation with relatively warm ground
temperatures from our 70s and 80s of the past couple of days. In
addition, it does not appear that the rate of snowfall will be that
significant so most of it will be melting on contact. If the rain/snow
persists longer into the evening, then we might see some light
accumulations on grassy areas but for now will not include in the
forecasts.

The main forecast issue after the precip ends Monday night will be
with the cold temperatures for both Tuesday and Wednesday mornings
with readings in the mid 20s north to the low 30s southeast. Some
of the guidance suggests clouds and wind will be a factor thru late
Monday night and if that is the case, especially across the east,
temps may be a bit too cold in that area. Return flow already setting
up by late Tuesday night into Wednesday across the west with slightly
warmer readings in that area, with the east looking to be the coldest
as the surface ridge axis will just to their east. Gusty south winds
will usher in warmer temperatures for Wednesday with afternoon highs
back into the 50s, which is still below normal for the middle of April.

LONG TERM...Thursday through Sunday

Still seeing some significant model differences with respect to
the systems for late in the week and weekend. The ECMWF is weaker
with the upper wave for late Thursday into Friday, but yet has
trended stronger with the shortwave digging southeast into the
Great Lakes for Easter Sunday. The last few runs of the GFS
ensemble have kept the precip chances going for late Thursday and
Friday and were not showing as much amplification with the upper
wave late next weekend with little in the way of precip for our
area. The better chances for showers will be late Thursday into
Friday with the first shortwave, but will hold on to only slight
chances for now for the system on Easter Sunday. Will have some
fluctuations with the temperatures ahead and behind these shortwaves
but overall, it appears we still may be averaging a bit below normal
as we head into the weekend, but it sure beats what we are going
to see tomorrow and Tuesday.

Smith


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$







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